Connection structure for coaxial connector and multilayer substrate

ABSTRACT

In the structure for connecting a board and a coaxial connector, which electrically connects a high-frequency board  20  mounted in an electroconductive casing  1  and a coaxial connector  10,  a transfer board  30  is disposed between the high-frequency board  20  and the coaxial connector  10,  and the high-frequency board  20  and the coaxial connector  10  are electrically connected through the transfer board  30.

TECHNICAL FIELD

The present invention relates to a connection structure between acoaxial connector and a multilayer board for use in, for example, ahigh-frequency circuit of a communication device and so on.

BACKGROUND ART

In a conventional connection structure between a coaxial connector and amultilayer board, the signal line pattern of the transmission line(hereinafter, referred to as ‘electroconductive pattern’) of ahigh-frequency multilayer board (hereinafter, referred to as ‘multilayerboard’) mounted in an electroconductive casing and the core wire of acoaxial connector have been directly electrically connected by use ofsuitable brazing material (see, for instance, JP-A-2001-177311).

The operation will now be described as below.

A high frequency signal input from the coaxial connector passes theconnection between the coaxial connector and the multilayer board, andpropagates through the transmission line formed on the multilayer board;and also in the propagating line in the direction opposite thereto, ahigh frequency signal that has propagated through the transmission linepasses the connection between the coaxial connector and the multilayerboard, and propagates toward the coaxial connector.

In the above operation, in the connecting portion between the coaxialconnector and the multilayer board, the spacing between the groundingface on the casing and the core wire of the coaxial connector becomeslarge because the multilayer board has its thickness, to thereby causethe impedance of the transmission line in this area to be greatlydisordered, and induce the transmission line to be dielectric. Here,there is a trend toward larger degree of the dielectric property thereofwith increasing thickness of the multilayer board. In addition, in themultilayer board, because it is difficult to form the transmission linepattern in the uppermost layer of this board and the ground pattern inthe layer located immediately under the layer closely to the end face ofthe board, a large pattern margin forms between the end face of theboard and the end of the ground pattern. For this reason, in thevicinity of the end face of the multilayer board, it is impossible toform the ground pattern constituting the transmission line. Therefore,there arises a problem that the impedance of the transmission line isgreatly disordered also in this area to thereby induce the transmissionline to be dielectric.

On this account, in the conventional connection structure between thecoaxial connector and the multilayer board, it is arranged that thecoaxial connector is equipped with a capacitive coaxial line in order tocancel the above-mentioned dielectric property of the transmission line,and thereby an impedance match is schemed to ensure its performancecapabilities.

The conventional connection structure between the coaxial connector andthe multilayer board has been arranged as mentioned above. As a result,around the frequencies designed such that the impedance match isprovided, the capacitive coaxial line provided on the coaxial connectorand the dielectric transmission line provided in the connection betweenthe coaxial connector and the multilayer board mutually cancel thecapacitive property and the dielectric property to thus render thematching. This reduces the disorder of impedance, thereby enabling theobtainment of a certain level of return-loss characteristic. However, atfrequencies away from the designed frequencies, the match cannot beprovided, and the disorder of impedance in the connection between thecoaxial connector and the multilayer board increases, thereby making itimpossible to obtain the low return-loss characteristic indispensable tothe high-frequency circuit. From these factors, in the conventionalconnection structure between the coaxial connector and the multilayerboard, it is very difficult to obtain favorable return-losscharacteristics over a wide frequency band. As a result, there is aproblem that countermeasures to development of broadband incommunication equipments seen in recent years cannot be implemented.

The present invention has been accomplished to solve the above-mentionedproblem. An object of the present invention is to provide a connectionstructure between a coaxial connector and a multilayer board that cangreatly reduce the disorder of impedance due to the electricalconnecting portion between the coaxial connector and the board, and thatcan obtain an excellent return-loss characteristic over a broad band.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention, there is provided aconnection structure between a coaxial connector and a multilayer board,the connection structure including: a casing; a coaxial connector thatis provided in this casing, and has a core wire; a multilayer board thatis provided in the casing, and has a first signal line pattern; atransfer board that is provided in the casing located between thismultilayer board and the coaxial connector, has a second signal linepattern, and that is formed so that the thickness of the transfer boardis smaller than the thickness of the multilayer board; a connectingmeans for electrically connecting the core wire of the coaxial connectorand the second signal line pattern; and a transmission line thatelectrically connects the first signal line pattern to the second signalline pattern, and suppresses an electromagnetic field distribution in aninward direction of the multilayer board.

According to another aspect of the present invention, there is provideda connection structure between a coaxial connector and a multilayerboard comprising: a casing in which an upper floor, a lower floor, and asidewall, which is adjacent to the upper floor, are formed; a coaxialconnector that is provided on the sidewall, and has a core wire; amultilayer board that is provided on the lower floor, and has a firstsignal line pattern; a transfer board that is provided on the upperfloor, and has a second signal line pattern; a connecting means forelectrically connecting the core wire of the coaxial connector and thesecond signal line pattern; and a transmission line that electricallyconnects the first signal line pattern to the second signal linepattern, and suppresses an electromagnetic field distribution in aninward direction of the multilayer board.

According to still another aspect of the present invention, there isprovided a connection structure between a coaxial connector and amultilayer board, wherein the transmission line is a coplanar-typetransmission line.

According to still another aspect of the present invention, there isprovided a connection structure between a coaxial connector and amultilayer board, wherein the multilayer board that has the first signalline pattern includes a microstripline-type transmission line or acoplanar-type transmission line.

According to still another aspect of the present invention, there isprovided a connection structure between a coaxial connector and amultilayer board, wherein the transfer board has a second backsideground pattern, and this second backside ground pattern and the secondsignal line pattern are electrically connected by use of a via holeformed on the side of the multilayer board.

Thereby, it is arranged that the transfer board, which electricallyconnects the high-frequency board mounted in the electroconductivecasing and the coaxial connector, be disposed between the board and theconnector. This eliminates the need for mounting a control-systemcircuit on the transfer board. Therefore, a single-layer-double-sidedboard can be used as the transfer board, thereby enabling the extremereduction of the thickness of the transfer board. As compared to theconventional connection structure in which the multilayer board and thecoaxial connector are directly electrically connected, it is possible toplace the signal line pattern of the transfer board and the core wire ofthe coaxial connector extremely closely to the grounding face. As aresult, the disorder of impedance in the transmission line can begreatly improved, to thereby ensure an excellent return-losscharacteristic in a broad band.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional side view of a connection structurebetween a coaxial connector and a multilayer board in accordance with afirst embodiment of the present invention.

FIG. 2 is a partially cutout plan view of FIG. 1.

FIG. 3 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board in accordance with a secondembodiment of the present invention.

FIG. 4 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board in accordance with a thirdembodiment of the present invention.

FIG. 5 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board, in accordance with a fourthembodiment of the present invention.

FIG. 6 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board in accordance with a fifthembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described withreference to the drawings in order to make description in further detailof the present invention.

Embodiment 1

FIG. 1 is a longitudinal sectional side view of a connection structurebetween a coaxial connector and a multilayer board in accordance with afirst embodiment of the present invention, and FIG. 2 is a partiallycutout plan view of FIG. 1.

As shown in FIG. 1 and FIG. 2, a coaxial connector 10 and a multilayerboard (high-frequency board) 20 are mounted on an electroconductivecasing 1, and a transfer or intermediate board 30 electricallyconnecting the both is disposed between the coaxial connector 10 and themultilayer board 20.

To explain in further detail, a connector-mounting hole 2 is prepared atthe sidewall of the casing 1, and the core wire 11 of the coaxialconnector 10 is inserted into this connector-mounting hole 2 through aninsulator 12. Moreover, the transfer board 30 is mounted on the innerwall of the casing 1. The transfer board 30 is constructed of adouble-sided board on the top surface of which a signal line pattern 31composing a microstripline-type transmission line is formed and on thebottom surface of which the ground pattern of a microstripline-typetransmission line (hereinafter, referred to as ‘ground pattern’) 32 isformed, and in the vicinity of the one end side of the transfer board(in the vicinity of the end portion of the board that is opposite to theconnector-mounting hole 2), a via hole 33 that electrically connects thetop surface layer of the board and the ground pattern 32 is provided.Here, the core wire 11 of the coaxial connector 10 inserted in theconnector-mounting hole 2, as mentioned above, extends to the upperportion of the signal line pattern 31 of the transfer board 30 mountedon the inner wall of the casing 1, and is electrically connected to thesignal line pattern 31 with a brazing material such as solder.

Further, the multilayer board 20 is mounted on the inner wall of thecasing 1 so as to be adjacent to the transfer board 30 on the side ofthe wall that is opposite to the connector-mounting hole 2. Themultilayer board 20 has a signal line pattern 21 constituting amicrostripline-type transmission line located on the top surfacethereof, the ground pattern 22 of the microstripline transmission linelocated on the board-internal layer (hereinafter, referred to as‘board-internal-layer ground pattern’), and a board-bottom-surfaceground pattern 23; and further, the multilayer board has a via hole 24that electrically interconnects these patterns 22, 23 and the topsurface of the board at one place near the transfer board 30.

Furthermore, on the top surfaces on the neighboring sides of themultilayer board 20 and the transfer board 30, the signal line patterns21 and 31 of both the boards are electrically connected each other bymeans of ribbon bonding or the like. Similarly, the via holes 24 and 33are mutually electrically connected by means of ribbon bonding or thelike. In such a way, a transmission line is formed such that the signalline pattern 31 of the transfer board 30 and the signal line pattern 21located on the top surface of the multilayer board 20, and the groundpatterns 22, 23, and 32 are electrically connected by coplanar-typetransmission lines 40, 40 a. Briefly, this transmission line constructsa high-frequency transmission line that is continuous by extendingacross the transfer board 30 and the multilayer board 20.

The operation will now be described as below.

A high frequency signal input from the coaxial connector 10 passes theconnecting portion between the core wire 11 of the coaxial connector 10and the signal line pattern 31 of the transfer board 30, propagatesthrough the microstripline-type transmission line 31 constructed of theabove-described signal line pattern, then passes the coplanar-typetransmission line 40, and subsequently propagates through themicrostripline-type transmission line 21 constructed of the signal linepattern formed on the multilayer board 20. Also in the case of thepropagating line in the opposite direction thereto, the high frequencysignal, which has propagated through the microstripline-typetransmission line constructed of the signal line pattern 21 formed onthe top surface of the multilayer board 20, passes the coplanar-typetransmission line 40, then propagates through the microstripline-typetransmission line constructed of the signal line pattern 31 formed onthe transfer board 30, passes the connection between the core wire 11 ofthe coaxial connector 10 and the signal line pattern 31 formed on thetransfer board 30, and propagates to the coaxial connector 10.

According to the first embodiment described above, it is arranged asfollows: the transfer board 30 is disposed between the multilayer board20 mounted in the electroconductive casing 1 and the coaxial connector10; the signal line pattern 31 formed on the transfer board 30 and thecore wire 11 of the coaxial connector 10 are electrically connected; andfurther, the signal line pattern 31 formed on the transfer board 30 andthe signal line pattern 21 formed on the tope surface of the multilayerboard 20 are electrically connected by the coplanar-type transmissionline 40. As a result, there is an effect that the disorder of impedancecan be greatly reduced, and an excellent return-loss characteristic canbe ensured over a broad band.

In other words, according to the above first embodiment, the disorder ofimpedance may be caused in the electrical connection between the coaxialconnector 10 and the transfer board 30; however, in contrast to thecircuit on the multilayer board 20, a control system circuit does notneed to be mounted on the transfer board 30. This enables the transferboard 30 to have an optimum board structure and design. Therefore, thethickness of the transfer board 30 can be extremely reduced. This canplace the signal line pattern 31 formed on the top surface of thetransfer board 30 much closer to the ground pattern 32 formed on thebottom surface thereof, and can also place the grounding face formed onthe casing much closer to the core wire 11 of the coaxial connector incomparison with the structure in which the multilayer board 20 iselectrically directly connected to the coaxial connector 10.Consequently, there is an effect that in this area the disorder ofimpedance of the transmission line is greatly improved.

In addition, in the multilayer board 20, it is difficult to form theinner-layer ground pattern 22 of the microstripline-type transmissionline to be close to the end face of the board, where the ground pattern22 is constructed of the signal line pattern 21 formed on the uppermostlayer thereof and the inner-layer ground pattern 22 located immediatelyunder the line pattern 21. For this reason, there exists a patternmargin M1 (see FIG. 1 and FIG. 2) between the end face of theinner-layer ground pattern 22 and the end face of the board. However,the transfer board 30 is constructed of a single-layered, double-sidedboard, not a multilayer board. Therefore, the employment of, forexample, an alumina substrate as the transfer board 30 enables the greatreduction of the pattern margin M2 between the end face of the groundpattern 32 formed on the bottom surface of the substrate and the endface to the substrate. Briefly, in the transfer board 30, it is possibleto form the ground pattern 32 located on the bottom surface thereofclosely to the end face of the board. For this reason, there is aneffect that the disorder of impedance of the transmission line in thevicinity of the end face of the board caused in the multilayer board 20can be greatly reduced. As a result, there is an effect that anexcellent return-loss characteristic over a broad band can be obtainedby the above-described connection or joining between the coaxialconnector 10 and the transfer board 30.

In contrast, if it is arranged that the signal line patterns 21, 31forming the microstripline-type transmission line that is common to thesurfaces of the multilayer board 20 and of the transfer board 30 areconnected to each other, so that the two boards 20, 30 may be connectedto each other, the pattern margin M1 of the internal layer of themultilayer board 20, the thickness of the multilayer board 20, and thethickness of the wall of the board gap become large. In this case, theimpedance is greatly disordered in the connected portion between boththe boards 20 and 30, and the excellent return-loss characteristiccannot be obtained.

However, according to the above first embodiment, the signal linepattern 31 formed on the transfer board 30 and the signal line pattern21 formed on the top surface of the multilayer board 20 are connected bythe coplanar-type transmission line 40 formed by means of ribbon bondingor the like. Thereby, the electromagnetic field in the connectionpropagates through the coplanar-type transmission line 40 to beconcentrated on the transmission line only, thereby greatly reducing thedistribution of the electromagnetic field in an inward direction of theboard. Therefore, the influence of the disorder of impedance is hardlyreceived, which may be caused by the transmission line in the vicinityof the end face of the multilayer board 20, depending on the presence orabsence of the internal-layer ground pattern 22 of the board multilayer20, the thickness of the wall of the board gap, and the thickness of themultilayer board 20. For this reason, there is an effect that afavorable return-loss characteristic can be obtained over a broad bandin the electrical connection between the above-described transfer board30 and the multilayer board 20 as well. As a result, there is an effectthat a favorable return-loss characteristic can be obtained over a broadband in the entire transmission line extending from the coaxialconnector 10 to the transfer board 30 and the multilayer board 20 aswell.

Embodiment 2

FIG. 3 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board according to a secondembodiment of the present invention. The same or equivalent parts as theones in FIG. 1 and FIG. 2 are designated by similar numerals to omit therepetitive explanation.

In the second embodiment, in the connection structure between thecoaxial connector and the multilayer board according to the above firstembodiment, it is arranged such that also in the vicinity of the endface of the transfer board 30 on the side of the coaxial connector 10,two coaxial-connector-to-transfer-board via holes 34 are provided,thereby electrically connecting the via holes 34 and theelectroconductive casing 1 by use of two transfer-board-connecting lines41 formed by means of ribbon bonding or the like.

According to the second embodiment of such a structure, a coplanar-typetransmission line is constructed by using the twocoaxial-connector-to-transfer-board connecting lines 41, which areelectrically connected from the two coaxial-connector-to-transfer-boardvia holes 34 to the electroconductive casing 1, and the core wire 11 ofthe coaxial connectors 10. As a result, the disorder of impedance can besuppressed still more effectively as compared to the case that performsthe electrical connection between the coaxial connector 10 and thetransfer board 30 by only the core wire 11 of the coaxial connector 10.Therefore, there is an effect that the return-loss characteristic can befurther improved as compared to the case in the above-mentioned firstembodiment.

Embodiment 3

FIG. 4 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board according to a thirdembodiment of the present invention. The same parts as the ones in FIG.3 are designated by similar numerals to omit the repetitive explanation.

In the third embodiment, in the connection structure between the coaxialconnector and the multilayer board according to the second embodiment,it is arranged that a coplanar-type transmission line 35 is formed onthe top surface of the transfer board 30 instead of the microstripline.

Thus, according to the above third embodiment, the connection structureis arranged so that the top surface of the transfer board 30 is providedwith the coplanar-type transmission line 35. Accordingly, thecoplanar-type transmission line is constructed of twocoaxial-connector-to-transfer-board connecting lines 41, which areconnected from the coaxial-connector-to-transfer-board via holes 34 tothe electroconductive casing 1, and the core wire 11 of the coaxialconnector 10. Thereby, when the electromagnetic wave is propagated fromthis coplanar-type transmission line to the transfer board 30, and alsowhen the electromagnetic wave is propagated in the opposite directionthereof, in either case, the propagation thereof can be always performedwhile keeping up the electromagnetic-field-transmission mode of thecoplanar type. For this reason, there is an effect that thedeterioration of the return-loss characteristic can be suppressed moreeffectively as compared to the case in the formation of themicrostripline-type transmission line on the top surface of the transferboard 30, which needs the conversion of theelectromagnetic-field-transmission mode between the microstripline typeand the coplanar type. Similarly, when the electromagnetic wave ispropagated from the transfer board 30 to the coplanar-type transmissionline 40, or also when the electromagnetic wave is propagated in theopposite direction, the propagation thereof can be always performedwhile keeping up the electromagnetic-field-transmission mode of thecoplanar type. Accordingly, there is an effect that the deterioration ofthe return-loss characteristic can be suppressed more positively ascompared to the case on the formation of only the microstripline-typetransmission line on the top surface of the transfer board 30, whichneeds the conversion of the electromagnetic-field-transmission modebetween the microstripline type and the coplanar type. Consequently,there is an effect that the return-loss characteristic can be improvedmore effectively in the third embodiment than in the above-mentionedsecond embodiment.

Embodiment 4

FIG. 5 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board according to a fourthembodiment of the present invention. The same parts as the ones in FIG.3 are designated by similar numerals to omit the repetitive explanation.

In the above third embodiment, the coplanar-type transmission line 35 issubstituted for the microstripline-type transmission line 31 used on thetransfer board 30 in the above second embodiment; however, in the fourthembodiment, a coplanar-type transmission line 25 is substituted for themicrostripline-type transmission line 21 used on the multilayer board 20in the above second embodiment.

According to the fourth embodiment, it is arranged that thecoplanar-type transmission line 25 replacing the microstripline-typetransmission line 21 according to the above second embodiment beprovided on the top surface of the multilayer board 20. Thus, when theelectromagnetic wave is propagated from the multilayer board 20 to thecoplanar-type transmission line 25, and also when the electromagneticwave is propagated in the opposite direction, in either case, thepropagation thereof can be always performed while keeping up theelectromagnetic field transmission mode of the coplanar type.Accordingly, there is an effect that the deterioration of thereturn-loss characteristic can be suppressed more effectively ascompared to the case on the formation of the microstripline-typetransmission line on the top surface of the multilayer board 20, whichneeds the conversion of the electromagnetic-field-transmission modebetween the microstripline type and the coplanar type. Therefore, thereis an effect that the return-loss characteristic can be improved moreeffectively in the fourth embodiment than in the above-mentioned secondembodiment.

Embodiment 5

FIG. 6 is a partially cutout plan view of a connection structure betweena coaxial connector and a multilayer board according to a fifthembodiment of the present invention. The same parts as the ones in FIG.3 are designated by similar numerals to omit the repetitive explanation.

In the fifth embodiment, it is arranged that coplanar-type transmissionlines 35 and 25 replacing the microstripline-type transmission lines 31and 21 according to the above second embodiment are formed on both thetop surfaces of the transfer board 30 and the multilayer board 20.

According to the fifth embodiment in which the coplanar-typetransmission lines 35 and 25 are thus formed on both the top surfaces ofthe transfer board 30 and the multilayer board 20, when theelectromagnetic wave is propagated from the coplanar-type transmissionline, which is constructed of the twoelectroconductive-casing-to-transfer-board connecting lines 41 connectedfrom the coaxial-connector-to-transfer-board via holes 34 to theelectroconductive casing 1 and the core wire 11 of the coaxial connector10, to the transfer board 30, and also when the electromagnetic wave ispropagated in the opposite direction, in either case, the propagationthereof can be always performed while keeping up the electromagneticfield transmission mode of the coplanar type. For this reason, there isan effect that the deterioration of the return-loss characteristic canbe suppressed more positively as compared to the case that is formedwith the microstripline-type transmission line on the top surface of thetransfer board 30 such that the conversion of theelectromagnetic-field-transmission mode between the microstripline typeand the coplanar type is necessary.

Further, when the electromagnetic wave is propagated from the transferboard 30 to the coplanar-type transmission line 40, and also when theelectromagnetic wave is propagated in the opposite direction, in eithercase, the propagation thereof can be always performed while keeping upthe electromagnetic-field-transmission mode of the coplanar type. Forthis reason, there is an effect that the deterioration in the returnloss characteristic can be suppressed more positively as compared to thecase that is formed with the microstripline-type transmission line.Furthermore, when the electromagnetic wave is propagated from themultilayer board 20 to the coplanar-type transmission line 40, and alsowhen the electromagnetic wave is propagated in the opposite direction,in either case, the propagation thereof can be always performed whilekeeping up the electromagnetic-field-transmission mode of the coplanartype. Consequently, there is an effect that the deterioration of thereturn-loss characteristic can be suppressed more effectively ascompared to the case formed with the microstripline-type transmissionline on the top surface of the multilayer board 20 such that theconversion of the electromagnetic-field-transmission mode between themicrostripline type and the coplanar type is necessary. Therefore, thereis an effect that the return-loss characteristic can be improved morepositively in the fifth embodiment than in the above-mentioned secondembodiment 2.

INDUSTRIAL APPLICABILITY

As mentioned above, a connection structure between a coaxial connectorand a multilayer board according to the present invention can be usedfor a high-frequency circuits and so on of communication apparatuses.

1. A connection structure between a coaxial connector and a multilayerboard comprising: a casing; a coaxial connector provided in this casing,and including a core wire; a multilayer board provided in the casing,and including a first signal line pattern, an inner-layer pattern, and apattern margin provided between an end face of the inner-layer patternand an end face of the multilayer board; a transfer board provided inthe casing located between the multilayer board and the coaxialconnector, the transfer board including a second signal line pattern, aground pattern, and a pattern margin provided between an end face of theground pattern and an end face of the transfer board, and the transferboard formed so that the thickness of the transfer board is smaller thanthe thickness of the multilayer board; connecting means for electricallyconnecting the core wire of the coaxial connector and the second signalline pattern; and a transmission line that electrically connects thefirst signal line pattern to the second signal line pattern, andsuppresses an electromagnetic field distribution in an inward directionof the multilayer board; wherein the pattern margin of the transferboard is smaller than the pattern margin of the multilayer board.
 2. Aconnection structure between a coaxial connector and a multilayer boardaccording to claim 1, wherein the transmission line is a coplanar-typetransmission line.
 3. A connection structure between a coaxial connectorand a multilayer board according to claim 1, wherein the multilayerboard that has the first signal line pattern includes amicrostripline-type transmission line or a coplanar-type transmissionline.
 4. A connection structure between a coaxial connector and amultilayer board according to claim 1, wherein the transfer boardincludes a top surface layer electrically connected by a via to theground pattern of the transfer board.
 5. A connection structure betweena coaxial connector and a multilayer board comprising: a casing formedof an upper floor, a lower floor, and a sidewall adjacent to the upperfloor; a coaxial connector provided on the sidewall, and including acore wire; a multilayer board provided on the lower floor, and includinga first signal line pattern, an inner-layer pattern, and a patternmargin provided between an end face of the inner-layer pattern and anend face of the multilayer board; a transfer board provided on the upperfloor, and including a second signal line patterns a ground pattern, anda pattern margin provided between an end face of the ground pattern andan end face of the transfer board; connecting means for electricallyconnecting the core wire of the coaxial connector and the second signalline pattern; and a transmission line that electrically connects thefirst signal line pattern to the second signal line pattern, andsuppresses an electromagnetic field distribution in an inward directionof the multilayer board; wherein the pattern margin of the transferboard is smaller than the pattern margin of the multilayer board.
 6. Aconnection structure between a coaxial connector and a multilayer boardaccording to claim 5, wherein the transmission line is a coplanar-typetransmission line.
 7. A connection structure between a coaxial connectorand a multilayer board according to claim 5, wherein the multilayerboard that has the first signal line pattern includes amicrostripline-type transmission line or a coplanar-type transmissionline.
 8. A connection structure between a coaxial connector and amultilayer board according to claim 5, wherein the transfer boardincludes a top surface layer electrically connected by a via to theground pattern of the transfer board.